No attribute "rotation_euler" on a KX_GameObject?
Details
A KX_GameObject has no attribute called &quot;rotation_euler&quot;.
What you request for is KX_GameObject.worldOrientation or KX_GameObject.localOrientation as you mentioned in your question description.
Be aware the orientation is a 3x3 matrix. The setter accepts Euler and a 3-tuple with Euler coordinates for your convenience. It will automatically convert it to a 3x3 matrix.
I'm pretty sure your observation of

[...] it rotated the object to a number which seemed independent of my input.

is not correct.
Answer
You answered your question by yourself: own.worldOrientation = (10, 10, 10).
Remarks:

A rotation matrix does not deal with angles, it is a linear equation system. It is a Cartesian coordinate system. You will never be able to directly read any angles from it. But you can convert the coordinates to a different coordinate system e.g. polar coordinates via mathutils' Matrix.to_euler(order, euler_compat).

Euler coordinates are angles given in rad (not degree). It is a Polar coordinate system.

The value 10rad will automatically reduced to the first period of the radian angle measure system's range (-pi ... +pi) which is -2.5664rad or -147°.

To convert degree to radian you can use the python library math e.g. math.radian